| 摘要 |
PURPOSE:To detect the rotating angle of a rotor precisely, by forming a magnet, in which a plurality of magnet pieces are arranged in a ring shape on the rotor of an ultrasonic wave motor, and detecting the passing of the magnet pieces by an optical sensor, which is provided so as to face the magnet piece. CONSTITUTION:Many magnet pieces 71 are arranged on the side of a rotor 5 of an ultrasonic wave motor facing a substrate 1 at a specified pitch in a ring shape. Thus a magnet 7 is formed. An annular magnet 6 is bonded on the substrate 1 so as to face the magnet 7. The rotor 5 is attracted by the base body 1. Magnet attracting members 81, 82... are provided between the magnet pieces 71, 72.... An optical sensor 11 is attached to the reference point of the annular magnet 6. When the rotor 5 is rotated, pulses are generated. The pulses generated by the optical sensor are measured, and the rotating angle of the rotor 5 is precisely detected. This device is suitable of the focusing mechanism of an AF camera. |
